/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.propertyeditors;

import java.beans.PropertyEditorSupport;
import java.io.File;
import java.io.IOException;

import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceEditor;
import org.springframework.util.Assert;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;

/**
 * Editor for {@code java.io.File}, to directly populate a File property
 * from a Spring resource location.
 *
 * <p>Supports Spring-style URL notation: any fully qualified standard URL
 * ("file:", "http:", etc) and Spring's special "classpath:" pseudo-URL.
 *
 * <p><b>NOTE:</b> The behavior of this editor has changed in Spring 2.0.
 * Previously, it created a File instance directly from a filename.
 * As of Spring 2.0, it takes a standard Spring resource location as input;
 * this is consistent with URLEditor and InputStreamEditor now.
 *
 * <p><b>NOTE:</b> In Spring 2.5 the following modification was made.
 * If a file name is specified without a URL prefix or without an absolute path
 * then we try to locate the file using standard ResourceLoader semantics.
 * If the file was not found, then a File instance is created assuming the file
 * name refers to a relative file location.
 *
 * 文件属性编辑器
 * 它支持Spring风格的URL:
 * 1.可以是"file:"或者"http:"前缀
 * 2.可以是"classpath:"前缀
 *
 *
 *
 * @author Juergen Hoeller
 * @author Thomas Risberg
 * @since 09.12.2003
 * @see java.io.File
 * @see org.springframework.core.io.ResourceEditor
 * @see org.springframework.core.io.ResourceLoader
 * @see URLEditor
 * @see InputStreamEditor
 */
public class FileEditor extends PropertyEditorSupport {

    private final ResourceEditor resourceEditor;


    /**
     * Create a new FileEditor,
     * using the default ResourceEditor underneath.
     *
     * 构造方法
     */
    public FileEditor() {
        this.resourceEditor = new ResourceEditor();
    }

    /**
     * Create a new FileEditor,
     * using the given ResourceEditor underneath.
     *
     * 构造方法
     *
     * @param resourceEditor the ResourceEditor to use
     */
    public FileEditor(ResourceEditor resourceEditor) {
        Assert.notNull(resourceEditor, "ResourceEditor must not be null");
        this.resourceEditor = resourceEditor;
    }


    /**
     * 设置
     *
     * @param text
     * @throws IllegalArgumentException
     */
    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        if (!StringUtils.hasText(text)) {
            setValue(null);
            return;
        }

        // Check whether we got an absolute file path without "file:" prefix.
        // For backwards compatibility, we'll consider those as straight file path.
        if (!ResourceUtils.isUrl(text)) {
            File file = new File(text);
            if (file.isAbsolute()) {
                setValue(file);
                return;
            }
        }

        // Proceed with standard resource location parsing.
        this.resourceEditor.setAsText(text);
        Resource resource = (Resource) this.resourceEditor.getValue();

        // If it's a URL or a path pointing to an existing resource, use it as-is.
        if (ResourceUtils.isUrl(text) || resource.exists()) {
            try {
                setValue(resource.getFile());
            } catch (IOException ex) {
                throw new IllegalArgumentException(
                        "Could not retrieve File for " + resource + ": " + ex.getMessage());
            }
        } else {
            // Create a relative File reference and hope for the best.
            setValue(new File(text));
        }
    }

    /**
     * 获取
     * 
     * @return
     */
    @Override
    public String getAsText() {
        File value = (File) getValue();
        return (value != null ? value.getPath() : "");
    }

}
